Sweep-based membrane gas separation integrated with gas-fired power production and CO2 recovery

Abstract

A process involving membrane-based gas separation and power generation, specifically for controlling carbon dioxide emissions from gas-fired power plants. The process includes a compression step, a combustion step, and an expansion/electricity generation step, as in traditional power plants. The process also includes a sweep-driven membrane separation step and a carbon dioxide removal or capture step. The carbon dioxide removal step is carried out on a portion of gas from the compression step.

We claim: 
     
       1. A gas separation and power generation process, comprising the following steps:
 (a) compressing an oxygen-containing stream in a compression apparatus, thereby producing compressed gas stream; 
 (b) combusting a first portion of the compressed gas stream with a gaseous fuel in a combustion apparatus, thereby producing a combusted gas stream; 
 (c) separating a second portion of the compressed gas stream in a gas separation apparatus adapted to selectively remove carbon dioxide, thereby producing a carbon-dioxide enriched stream and a carbon-dioxide-depleted stream; 
 (d) routing the carbon-dioxide-depleted stream and the combusted gas stream as first and second working gas streams to a gas turbine apparatus mechanically coupled to an electricity generator, and operating the gas turbine apparatus, thereby generating electric power and producing a turbine exhaust stream; 
 (e) passing at least a first portion of the turbine exhaust stream to a membrane separation step, wherein the membrane separation step comprises:
 (i) providing a membrane having a feed side and a permeate side, and being selectively permeable to carbon dioxide over nitrogen and to carbon dioxide over oxygen, 
 (ii) passing the first portion of the turbine exhaust stream across the feed side, 
 (iii) passing air, oxygen-enriched air, or oxygen as a sweep stream across the permeate side, 
 (iv) withdrawing from the feed side a residue stream that is depleted in carbon dioxide compared to the turbine exhaust stream, 
 (v) withdrawing from the permeate side a permeate stream comprising oxygen and carbon dioxide; and 
 
 (f) passing the permeate stream to step (a) as at least a portion of the oxygen-containing stream. 
 
     
     
       2. The process of  claim 1 , wherein the gas separation apparatus is a membrane separation apparatus. 
     
     
       3. The process of  claim 1 , wherein the gas separation apparatus is an absorption apparatus. 
     
     
       4. The process of  claim 2 , wherein the membrane separation apparatus incorporates molten salt membranes. 
     
     
       5. The process of  claim 2 , wherein the membrane separation apparatus incorporates polymeric membranes. 
     
     
       6. The process of  claim 2 , wherein the membranes separation apparatus incorporates ceramic membranes. 
     
     
       7. The process of  claim 3 , wherein the absorption apparatus uses an amine-based sorbent. 
     
     
       8. The process of  claim 3 , wherein the absorption apparatus uses a carbonate-based sorbent. 
     
     
       9. The process of  claim 1 , further comprising cooling the second portion of the compressed gas stream before routing it to the gas separation apparatus. 
     
     
       10. The process of  claim 1 , further comprising cooling the turbine exhaust stream before passing it to the membrane separation step. 
     
     
       11. The process of  claim 1 , further comprising routing a third portion of the compressed gas stream as a third working gas stream to the gas turbine apparatus of step (d). 
     
     
       12. The process of  claim 1 , wherein the gaseous fuel comprises natural gas. 
     
     
       13. The process of  claim 1 , wherein the gaseous fuel comprises syngas. 
     
     
       14. The process of  claim 1 , further comprising routing the turbine exhaust stream to a heat recovery steam generator before carrying out step (e). 
     
     
       15. The process of  claim 1 , wherein the residue stream has a carbon dioxide concentration of less than 1 vol %. 
     
     
       16. The process of  claim 1 , wherein the carbon-dioxide-enriched stream has a carbon dioxide concentration of at least 90 vol %. 
     
     
       17. The process of  claim 1 , wherein the carbon-dioxide-depleted stream contains at least 5 vol % carbon dioxide. 
     
     
       18. The process of  claim 1 , wherein a second portion of the turbine exhaust stream is withdrawn upstream of the membrane separation step and recirculated to step (a) for recompression in the compression apparatus. 
     
     
       19. The process of  claim 1 , wherein:
 (A) step (a) is carried out such that the compression apparatus comprises a first compressor and a second compressor, the first compressor producing a first compressed gas stream and the second compressor producing a second compressed gas stream; 
 (B) step (f) is carried out by passing the permeate stream to the first compressor; 
 (C) the first compressed gas stream is combusted as the first portion in step (b); 
 (D) a second portion of the turbine exhaust stream is withdrawn upstream of the membrane separation step and directed to step (a) for compression in the second compressor; 
 (E) the second compressed gas stream is separated as the second portion in step (c). 
 
     
     
       20. A gas separation and power generation process, comprising the following steps:
 (a) compressing an oxygen-containing stream in a first compression apparatus, thereby producing a first compressed gas stream; 
 (b) compressing a carbon-dioxide-containing gas stream in a second compression apparatus, thereby producing a second compressed gas stream; 
 (c) combusting the first compressed gas stream in a combustion apparatus, thereby producing a combusted gas stream; 
 (d) separating the second compressed gas stream in a gas separation apparatus adapted to selectively remove carbon dioxide, thereby producing a carbon-dioxide enriched stream and a carbon-dioxide-depleted stream; 
 (e) routing the carbon-dioxide-depleted stream and the combusted gas stream as first and second working gas streams to a gas turbine apparatus mechanically coupled to an electricity generator, and operating the gas turbine apparatus, thereby generating electric power and producing a turbine exhaust stream; 
 (f) passing at least a first portion of the turbine exhaust stream to a membrane separation step, wherein the membrane separation step comprises:
 (i) providing a membrane having a feed side and a permeate side, and being selectively permeable to carbon dioxide over nitrogen and to carbon dioxide over oxygen, 
 (ii) passing the first portion of the turbine exhaust stream across the feed side, 
 (iii) passing air, oxygen-enriched air, or oxygen as a sweep stream across the permeate side, 
 (iv) withdrawing from the feed side a residue stream that is depleted in carbon dioxide compared to the turbine exhaust stream, 
 (v) withdrawing from the permeate side a permeate stream comprising oxygen and carbon dioxide; 
 
 (g) passing the permeate stream to step (a) as at least a portion of the oxygen-containing gas; and 
 (h) passing a second portion of the turbine exhaust gas to step (b) as at least a portion of the carbon-dioxide-containing gas. 
 
     
     
       21. The process of  claim 20 , further comprising routing the turbine exhaust stream to a heat recovery steam generator before carrying out steps (f) and (h). 
     
     
       22. The process of  claim 20 , wherein the gas separation apparatus comprises a membrane separation apparatus. 
     
     
       23. The process of  claim 20 , wherein the gas separation apparatus comprises an absorption unit. 
     
     
       24. The process of  claim 20 , wherein the residue stream has a carbon dioxide concentration of less than about 1 vol %. 
     
     
       25. The process of  claim 20 , wherein the carbon-dioxide-enriched stream has a carbon dioxide concentration of at least about 90 vol %.